Study design: within-subject cross-over double-blind placebo controlled study. Study population: 48 current smokers, male, age 25-40, at least smoking 10 cigarettes /day the last year, in general good health. Additional criteria; 1) No contra-indications for MRI 2) No history of cognitive deficits or brain trauma 3) No use of psychoactive medication 4) No contra-indications for nicotine gum.